Behold a visual history of Hard Drive icons in the parallel worlds of Windows and Mac. Notice how they get more and more realistic without becoming more meaningful. Personally I prefer the balance between abstraction and a tactile feel found in the Win9x/W2k and MacOS 9 versions.
The old Mac (v6 and before, I think) icon is pretty impressive and to someone who hasn't opened up their computer, just as meaningful as any of the other icons.
Photorealism is the dumbest idea of all. So that's what a hard drive looks like.
Here's the equivalent chart of folder icons. Very similar parallels, problems, and progression to the hard drive icons.